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Yet Another Power Over Ethernet

Yet Another Power Over Ethernet

A friend of mine aquired a pair of DLink DWL-900APs which he wanted for a 2.5km point to point link with above 2Mbit speed. So I undertook to make him a Power Over Ethernet kit. As the DWL-900AP needs 5V to operate, I have included regulation so that the AP will get consistent power over a variety of CAT5 cable lengths. This POE IS NOT compatible with the IEEE 802.3af POE standard.
Once it’s all assembled start off by plugging in the 12V PSU to the bottom end. The LED should come on. Hook the two POE boxes together with regular CAT5. It must not be a crossover cable. If you are unsure about the correct CAT5 wiring, see here. With the two POEs hooked up the top LED should come on. Using a multimeter, place the ground probe on the centre pin or the casing of the 7805. With the red probe test the left pin (pin 1) – it should show approximately 11-12V on it. Test the right pin (pin 3) and it should show 4.9 to 5V.

With the multimeter ground probe still on the 7805 ground, check each CAT5 pin on the top and bottom connectors to ensure there has been no miswiring. You should read no voltage whatsoever on the CAT5 connectors. The power should only appear on the segment between the POE boxes.


With the power disconnected test the continuity between the bottom and top CAT 5 connectors. Pins 1 (orange white), 2 (orange), 3 (green-white) and 6 (green) should run straight through unimpeded between both connectors. These four wires are the two pairs ethernet uses. On the POE in between the boxes pins 4 and 5 (blue) and 7 and 8 (brown) is used to carry the power.

Finally, with the multimeter and the power on test the top end power connector to see that 5V is appearing on the centre pin.

Once you are confident of your wiring, plug in the AP and the bottom end to your hub/switch. If you want to hook the bottom end directly to an ethernet card, simply swap the orange and green pairs on the connector when you crimp it, or when you wire up the bottom end box. Either “ping” the AP or use the SNMP tools to see you you have a working connection to it.

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